They tell you to have caution.
protons and electrons are both always the atomic number which is 9 in this case.
For neutrons you subtract the atomic number (9) from the weight of the atom (18.998) some teachers will want you to round to the nearest whole (19). We do this because the number of protons is the atomic number so if you subtract the protons from the whole weight of the atom you would have the electrons and neutrons left. Since electrons weigh so little we don't have to subtract them. Weighing neutrons and electrons would be like weighing an elephant (neutrons) and then putting one marshmallow on the scale (electron).
The correct answer is option B. The most dense phase of matter is the solid phase and the least dense are gases. However, there is an exception. Water is the exception. Solid water or ice is less dense than the liquid phase therefore it floats on liquid water.
D will because water just turns from liquid to a gas by adding heat. That is a physical change. The other equations are chemical changes.
So for D you have to find energy right
from c you get wavelength Lambda
so on D use this
E = Hc / lambda
c is given 1.5 x 10 ^20
h = 6.624 x 10^-34
and then you get answer for energy
